In the field of air traffic control, the safety distances between airplanes, standards dictated by the ICAO (International Civil Aviation Organization), have been established so as to avoid the dangers related to the encountering by airplanes of the wake turbulence (or “Wake Vortex” as it is also known) generated by an airplane in front of them. Such turbulence is indeed particularly dangerous when the airplane which passes through it is in a situation of vulnerability, such as that which it experiences during the takeoff and landing phases, in particular at the point of entry into the ILS (i.e. “Instrument Landing System”) guidance zone for runway approach on landing, while it is situated a relatively small distance from the ground and in relatively congested navigation zones.
Currently, for safety reasons, and because the evolution of such turbulence over time is relatively poorly known, the distances separating two aircraft, imposed by the ICAO, correspond to significant safety margins. These safety distances do not in particular take into account meteorological conditions (natural turbulence of the atmosphere) which condition the rate of fading of the phenomenon, nor the aerological conditions (crosswind for example) which condition its movement through space.
Faced with the constant and rapid increase in air traffic and with the arrival of new wide-bodied airplanes (Airbus A380 and Boeing B747-8), a dual problem arises related to the following two conflicting constraints:                a first constraint gives expression to the fact that a wide-bodied airplane produces greater wake turbulence than a medium-bodied or narrow-bodied airplane. Hence, and in the absence of complementary parameters, the safety distance that must be complied with by an airplane which is following a wide-bodied craft must naturally be, in absolute terms, greater than in the case where the same airplane is following a medium-bodied or a narrow-bodied craft; in particular in the takeoff and landing phase. This constraint results in a predictable lengthening of the waiting times during takeoffs and landings for airplanes situated behind a wide-bodied craft.        a second constraint gives expression to the fact that in order to handle ever greater air traffic, it is necessary to accelerate the rotations so as to avoid clogging up air terminals.        
Faced with these conflicting constraints, one solution consists in complicating the airport infrastructures so as to allow aircraft to follow, both on takeoff and on landing, diversified trajectories (corridors), so that two airplanes can follow one another relatively closely by moving along different takeoff or landing axes allowing each airplane not to pass through the wake of the airplane in front while the wake turbulence is still dangerous. However this solution, in addition to the fact that it requires the installation of relatively sophisticated guidance equipment, lacking in many airports, furthermore does not make it possible to determine whether the safety distance applied in this or that circumstance is a just sufficient distance or whether conversely it is too widely estimated.
Another known solution consists in trying to detect the presence of wake turbulence and the distance of such turbulence by means of sensors. Various types of sensors have been studied for the detection of wake turbulence, and in particular the Doppler Lidar, pulsed Laser emission systems making it possible to carry out a Doppler measurement. The major drawback of this type of sensor for operational use is that it can only operate correctly in clear weather. In fog and rain, the Lidar can no longer be employed. Moreover the Lidar, although possessing good angular resolution, better in particular than a Radar, has lower distance and Doppler resolutions. In particular, the Lidar is incapable of measuring certain details on the geometry of the turbulence spiral which make it possible in particular to determine its state of fading so that insufficient knowledge of the detected turbulence is obtained. Moreover, current Lidar systems are not able to monitor, in a time span compatible with operational requirements, a sufficiently wide sector of space to allow effective monitoring of an airport zone.